What is placenta previa?
Placenta previa is a problem with the placenta during pregnancy. The placenta is a round, flat organ that forms during pregnancy to give the baby food and oxygen from the mother. The placenta forms on the inside wall of the uterus soon after conception.
During a normal pregnancy, the placenta is attached higher up in the uterus, away from the cervix . But in rare cases, the placenta forms low in the uterus. If this happens, it may cover all or part of the cervix. When the placenta blocks the cervix, it is called placenta previa.
See pictures of a normal placenta and placenta previa .
What causes placenta previa, and how can you lower your risk?
Doctors aren't sure what causes placenta previa. But there are things that raise a woman’s risk of it. These things are called risk factors. Some risk factors you can control to lower your risk. Others are things you can't control.
Risk factors for placenta previa that you can control include:
Risk factors that you can't control include:
If your doctor finds out before your 20th week of pregnancy that you have a placenta that is attached low in the uterus, chances are good that it will get better on its own. In fact, 9 out of 10 cases found before the 20th week go away on their own by the end of the pregnancy. 1 This is because as the lower uterus grows, the position of the placenta can change. So by the end of the pregnancy, the placenta may no longer block the cervix.
What are the symptoms?
Some women with placenta previa do not have any symptoms. But there are a few warning signs. If you have placenta previa, you may notice one or more symptoms. These include:
Call your doctor or go to the nearest emergency room right away if you have:
How is placenta previa diagnosed?
Most cases of placenta previa are found during the second trimester when a woman has a routine ultrasound . Or it may be found when a pregnant woman has vaginal bleeding and gets an ultrasound to find out what is causing it. Some women find out that they have placenta previa only when they have bleeding at the start of labor.
How is it treated?
The kind of treatment you will have depends on:
If you have placenta previa and aren't bleeding, it is important to avoid having sex or vaginal exams and to avoid putting anything else in your vagina. (But you may have a carefully done vaginal exam at the hospital.) You should see your doctor if you have any bleeding.
If you are bleeding, you may have to stay in the hospital. When your baby is mature enough, or if too much bleeding is putting you or your baby in danger, your baby will be delivered. Doctors always do a cesarean section when there is a placenta previa. This is because the placenta can be disturbed with a vaginal delivery, and it can cause severe bleeding.
What are the possible problems from having placenta previa?
Placenta previa can cause problems for both the mother and the baby. These include:
Frequently Asked Questions
Symptoms of placenta previa include one or both of the following:
Bleeding from placenta previa may taper off and even stop for a while. But it nearly always starts again days or weeks later.
Some women with placenta previa do not have any symptoms. In this case, placenta previa may only be diagnosed by an ultrasound done for other reasons.
Exams and Tests
An ultrasound test is used to diagnose a low-lying placenta or placenta previa, in which the placenta partially or fully covers the cervix . But ultrasound does not always provide a clear picture of the placenta's location.
Unless an immediate cesarean delivery is planned, a pelvic (vaginal) examination is not done because of the risk of further injuring the placenta, causing heavier bleeding.
Electronic fetal heart monitoring is used to check the fetus's condition.
When an early delivery is needed, an amniocentesis may be done. It is used to find out whether the fetus's lungs are ready to breathe well after birth. For an amniocentesis, a needle is inserted into the mother's belly to take a small sample of amniotic fluid from inside the uterus. This fluid is made by the fetus's lungs. A lab test of the fluid can test for signs that the lungs are well developed.
If you have placenta previa, your treatment will depend upon:
If you have placenta previa and begin to bleed, you may be hospitalized. If your fetus is mature, you will have a cesarean delivery. If your bleeding slows down or stops, delivery can most likely be delayed. This watching and waiting approach is called expectant management. The course of expectant management is based on your and your fetus's condition.
Delivery involving placenta previa is done by cesarean section.
About 25 out of 100 women with placenta previa deliver their babies preterm (before the 37th week of pregnancy). 3 Infant problems following placenta previa are usually related to prematurity. If your infant is premature, he or she may need care in a neonatal intensive care unit, or NICU. Care in the NICU can last days or weeks, depending on the extent of a baby's problems and the amount of care needed. For more information, see the topic Premature Infant.
Treatment for placenta previa can be done by:
Treatment for a premature infant can be provided by a neonatologist .
If you have placenta previa and are not bleeding, it is important to follow certain precautions:
Call 911 or other emergency services right away if you have severe vaginal bleeding. Severe vaginal bleeding means you are passing blood clots and soaking through your usual pad each hour for 2 or more hours (you should not be using tampons).
Call your doctor now or go to the closest emergency room right away if you have any vaginal bleeding.
If you have had placenta previa
After you have had placenta previa, you may have questions about a future pregnancy. Based on the nature of your condition, your doctor will be able to answer your questions and address your concerns.
In very rare cases, placenta previa causes a stillbirth or newborn death. Should you experience such a loss, allow yourself time to grieve. Expect that your partner, children, and other family members may also be deeply affected. Consider meeting with a support group, reading about the experiences of other women, and talking to friends, a counselor, or a member of the clergy to help you and your family cope with your loss. For more information, see the topic Grief and Grieving.
Other Places To Get Help
Last Revised: February 3, 2012
Miller DA (2010). Placenta previa and abruption placentae. In Management of Common Problems in Obstetrics and Gynecology, 5th ed., pp. 57–61. Chichester: Wiley-Blackwell.
Kay HH (2008). Placenta previa and abruption. In RS Gibbs et al., eds., Danforth's Obstetrics and Gynecology, 10th ed., pp. 387–399. Philadelphia: Lippincott Williams and Wilkins.
Scearce J, Uzelac PS (2007). Third-trimester vaginal bleeding. In AH DeCherney et al., eds., Current Diagnosis and Treatment Obstetrics and Gynecology, 10th ed., pp. 328–341. New York: McGraw-Hill.
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